It is sometimes necessary to extract chronically implanted medical devices, particularly endocardial leads for use with pacemakers and implantable cardioverter-defibrillators (ICDs), if such leads fail or should infection develop.
Removal of such implanted devices presents several obstacles. For example, fibrous tissue growth along any portion of a cardiac lead may hamper extraction and can lead to trauma in adjacent cardiovascular tissues.
Various methods have been developed to remove chronically implanted devices. For cardiac leads, a common removal method is traction, wherein a longitudinal force is applied to the lead body after exteriorizing the proximal end of the lead. However, complications and difficulties encountered when using traction have prompted development of surgical approaches and intravascular counterpressure and countertraction (Love et al. PACE 2000 23:544-551).
Surgical approaches involve exposing the heart and great veins via sternotomy or thoracotomy followed by extraction of the lead via a transmural incision in the atrium or ventricle. While this removal technique is generally successful, it requires skills not generally available and is associated with morbidity and high cost (Love et al. PACE 2000 23:544-551).
In cardiovascular countertraction, a sheath made of polymer or metal slides distally over the lead body. A locking stylet may be passed through the interior of the lead and locked at the lead tip to localize traction forces at the tip. Traction applied to the lead pulls ingrown tissue to the sheath. Traction force is countered by the tip circumference of the sheath which applies a localized shear stress on the fibrotic tissue, separating it from the lead body. (Ellenbogen, Kenneth A., and others, ed. Clinical Cardiac Pacing, Defibrillation, and Resynchronization Therapy (Philadelphia, Pa. Saunders Elsevier, 2007), 885-886.)
Counterpressure is a similar extraction technique used when calcified tissues are present in which countertraction force is converted to pressure localized between the edge of the sheath and adjacent tissues. This pressure peels calcified masses from the vein and/or heart walls, thus damaging the tissues (Ellenbogen, 2007, 886).
Alternative sheaths include those using powered, mechanical cutting tips, RF ablation and laser vaporization. (Ellenbogen, 2007, 886-890.) However, each method is associated with significant risks. Therefore there is a need for an alternative and safer method of extracting medical devices from a patient.